The present invention relates to a method of controlling access to an area accessible by persons, particularly to a space closed by a door. For performance of the method there is provided a mobile communications unit, on which at least one access code is filed, and a receiver unit for receiving the access code. The access code is transmitted from the communications unit to the receiver unit. The receiver unit thereupon checks the access code and frees the access if the check is successful.
In the case of modern access control systems use is frequently made, for identification of persons, of contactlessly operating RFID (Radio Frequency Identification) systems. An RFID system of that kind comprises a transponder and a mobile or stationary RFID reader. If an RFID reader transmits a radio signal and the transponder, which substantially consists of a microchip and an antenna, is disposed in the vicinity, i.e. at a spacing from a few centimeters to some meters, the transponder responds and communicates the data stored thereon, for example an access code, to the reading station. RFID systems of that kind are frequently used in destination call terminals of elevator installations. However, in that case the disadvantage exists that the RFID systems have to permanently radiate an electromagnetic field for establishing contact with the transponder and thus they consume a comparatively large amount of electrical energy.
An elevator installation with a recognition system for recognition of a call issued on a floor is known from European patent EP 0 699 617 B1. This call is supplied to a control unit which determines an elevator by means of an allocation algorithm and informs the user of this elevator. The recognition devices, which are each arranged in stationary position in the access region to the elevators on the respective floor and which are also termed destination call terminals, permanently radiate an electromagnetic field. As soon as an information transmitter carried by the user comes into the electromagnetic field the information transmitter is awakened as a consequence of the electromagnetic field and transmits the data stored thereon, such as, for example, an identification code, to the recognition device.
However, in the afore-described elevator installation the disadvantage results that the recognition devices located at the individual floors permanently radiate an electromagnetic field in order to make it possible to establish contact with the information transmitter.